High-frequency heating apparatus



July 30, 1946. 11 su 2,405,037

HIGH FREQUENCY HEATING APPARATUS Filed March 17, 1944 4 2 Sheets-Sheet l Inventor: Eugene T. Hsu,

'July 30, 1946'. E. T. HSU 2,405,037

HIGH .FREQUENGY HEAT ING APPARATUS Filed March 17, 1944 2 Sheets-Sheet 2 Fig.5

' Inventor: Eugene T. Hsu,

b ya b41444 is Attorne Patented July 30, 1946 UNITED, STATES PATENT OFFICE 2,405,037 HIGH-FREQUENCY HEATING APPARATUS Eugene T. Hsu, Schenectady, N. Y., assignor to General Electric Com New York pany, a corporation of.

Application March 17, 1944, Serial No. 526,925

Qlaimn, (Cl. 219-. -47) My invention'relates to high frequency -.electric heating'apparatus, more particularly to high frequency induction heating apparatus'for continuously heating elongated or strip dielectric material, and has for its object a simple, reliable and efiicient heating apparatus of this type.-

More particularly, my invention relates to heating-apparatus for'heating elongated dielectric materialshaving relatively small cross sections, suchas in the form of cord,-yarn, thread or thin strips. The materials. maybe organic or inorganic, such as cotton, Wool, cellulose plastic, rubber, glass, etc;

In carrying out my invention in one form, I

of-the electrodes adjacent each other for concentrating the electrostatic field'along the length of the material whereby the material is very efficiently heated throughout by electrostatic induction, i. e., dielectric loss or molecular friction.

For amore complete understanding of my invention; reference should be had to the accompanying drawings, Fig. ;1 of which is the'front elevation view-partly in section of an'electrode em-- bodying-myinvention; Fig.2 is a partly diagram matic side elevation -view of heating apparatus for threadlike materials embodying my invention; Fig. 3 is a viewsimilar to Fig.1 but showing the electrodes providedwith slots for the pas sage therethroughof strip material; Fig. 4 is a partial vview similar to Fig.- 2 showing a settingr' apparatus embodying the electrodes shown in;

Fig.3; While Fig; 5 is a plan view of Fig. 4 to a reduced scale.

Referring to Figs, 1 and;2 of the drawings,-

in-oneform of my invention 1- provide'two plate shaped electrodes l0 and-ll eachof which is provided with a transversely extending aperture l2, which electrodes are suitably secured --as by bolts [3 and {4 to a support I 5 made of a; suitable electrically insulating material such as rub.-

ber-or porcelain. The plates made of suitable;

electrically conducting material, such as-copper r or aluminum, are suitably spaced apart and-arc electrically connected to the terminals of a suitable high frequency oscillator 16, preferably of the electric discharge device type.

An important-feature of my invention is the provision of annularor tubularelectrostatic field concentrating projections l1 and I8 on the electrodes around the apertures 12; As shown, these projections are in effect tubular extensions of the electrodes around the apertures. All edges of the tubular extensions .should be rounded and the projections may be substantially hemispherical in shape. These projections serve the purpose of directing and concentrating the electrostatic field along the length of the-threadlike article is extending. between the .tWoelectrodes so that this length of the article is in the-field and surrounded by the field and is therebyheated quickly by the electric, energy dissipated-as heat Within the body of the article itself by dielectric loss. As shown, they thread I!) is passed from the roll 28 to the roll 2| by means of suitable driving means (not shown) for the rolls. From the roll 2d, the thread ;is directed'by a seriesof rolls 22 downward through a suitable impregnating liquid 22a, such as a rubber or cellulos plastic material which liquid eithercoats or impregnates the material, such as cotton, of the thread. In passing between the two plates, the thread-is heated to a temperature-high enough to vulcanize or set the material with which it is treated. A suitable tension is maintainedcn the-thread so as to hold it,

as shown, in spaced relation with the walls of the holes throughthe electrodes. The-thread is maintained in a central position with respect to theholes, as shown.

Any suitabl spacing'between the electrodes and frequency of thecurrent supplied to the elec- ,trodes may be used-although the spacing between the, electrodes and the size of electrodes are dependent upon the frequency used. In a typical heater the-two electrodes were spaced apart approximately, two inches and current was supplied. to 4 them having a frequency, of approximately 40,000,000 cyclesa secondgandxa voltageof approximately-2500.

I contemplate that each-electrode may be.pro-

vided with-a plurality of-holes 12, as shown in Fig. ;2, whereby, a plurality of strands of material may be'passed between two electrodes having similar apertures. As shownrin Fig; 1, the electrode is elongated horizontally in ,the'plane of the drawing and :provided with a single row of holes which mayrbe'of diflierent-sizes. Obviously,

any suitable arrangement-of the holes maybe used.-- The number-of gholes, each with its own field concentrating projection as previously de.--= scribed, ;will of course be 1 dependent upon the size of the electrode, and the size of the electrode in turn is dependent upon the frequency of the electric current supplied to the electrodes. When a plurality of holes are used, it is important that the electrodes be maintained in parallel relation with each other so that electrostatic fields of uniform strength are maintained between the projections l1 and I8 of each opposed pair.

For purposes of adjustment in a vertical direction, I have shown the electrodes provided each with a vertical slot 23 through which its clamping bolt extends, whereby by loosening the bolt the electrode can be adjusted vertically with respect to the thread so as to bring the thread in the center of the hole.

I have also shown projections 24 and 25, simi-- lar to the projections l! and H3, on the opposite sides of the electrodes, i. e., on the outer nonadjacent sides, although these projections are not absolutely necessary because most of the lines of force concentrate between the electrodes.

In the modified form of my invention shown in Figs. 3, 4 and 5, the electrodes are provided with opposite semi-cylindrical portions 28 and 21, each of which is provided with a slot 28 through which the strip material 29 is passed continuously. Thus, as shown, the convex sides of the semicylindrical portions 26 and 2'! are adjacent each other, whereby they form projections to direct and concentrate the electrostatic flux into the strip 28. In this modified form of my invention, the lower ends of the electrodes are provided with lateral extensions, horizontal as seen in the drawing, having a slot 39 through which extends the clamping bolt 3 l By loosening the bolt, the electrode can be adjusted with respect to the other electrode, thereby to vary the spacing between them and also bring them into parallel relation with each other.

The strip material 2!] of this form of my invention may, as described in connection with Figs. 1 and 2, be made from a fibrous material which is impregnated with a rubber or cellulose plastic material and then passed between the plates and heated to set the rubber or plastic, or it may be a rubber or plastic strip.

As with the form shown in Figs. 1 and 2, the slotted electrodes of Figs. 3, 4 and 5 can be provided with any suitable number of slots for the simultaneous heatin of a plurality of strips. As shown, each electrode is provided with two slots whereby two strips can be heated.

It will be understood that the annular projecting portions H and iii are the effective portions of the electrodes. When a single strand or thread is to be heated any suitable electrically insulating support may be provided for these annular portions, the plate portion being omitted. Moreover the openings or apertures in the electrodes may be in the form of slots so that the material may be initially moved sidewise into the openings without threading through the openings.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claim to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Electric heating apparatus comprising a pair of spaced apart plate electrodes, an electrostatic field concentrating projection on each of said electrodes provided with a central aperture, said projections being oppositely disposed with respect to each other on adjacent sides of said electrodes, and electric connections for supplying high frequency current to said electrodes thereby to produce a high frequency electrostatic field between said projections and in an article to be heated extending through said apertures between said projections.

2. Electric heating apparatus for the continuous heating of elongated dielectric material comprising mean for moving the material to be heated along a predetermined path, a pair of electrodes spaced apart along said path of movement, each of said electrodes being provided with an opening through which said material extends, a projection on each of said electrodes on the side adjacent the other electrode and surrounding the opening in said electrode, and electric connections for supplying a high frequency current to said electrodes thereby to produce a high frequency electrostatic field between said projections and in said material whereby said material is heated.

3. Electric heating apparatu for the continuous heating of a thread of dielectric material comprising two electrodes made of electrically conducting material, a substantially annular projection on each of said electrodes provided with a central longitudinal aperture extending through the e ectrode, said annular projections being secured to adjacent sides of said electrodes,

a support on which said electrodes are secured in electrically insulated spaced relation with each other, and electric connections for supplying a high frequency current to said electrodes having a frequency of at least substantially 40 million cycles a second thereby to produce a high frequency field between said projections and in a thread of dielectric material passed through said apertures.

4. Electric heating apparatus for the continuous heating of threads of dielectric material comprising two plate electrode made of electrically conducting material, each of said electrodes bein provided with a plurality of apertures, electric field concentrating projections on each of said electrodes surrounding each of said apertures on the side adjacent the other electrode, an electrically insulating support on which said electrodes are secured in a predetermined spaced relation with each other, and electric connections for supplying a high frequency current to said electrodes thereby to produce a high frequency field between said projections and in a plurality of threads of dielectric material passed through pairs of opposite apertures in said plates.

5. Electric heating apparatus for the continuous heatin of elongated strip dielectric material comprising two electrodes made of electrically conducting material, a'substantially semicylindrical portion on each of said electrodes provided with a central longitudinal slot, the convex sides of said semicylindrical portions being adjacent each other, a support made of electrical y insulating material on which said electrodes are secured in a predetermined spaced relation with each other, and electric connections for supplying a high frequency current to said electrodes having 7 a frequency of at least substantially 40 million cycles a second thereby to produce a high frequency field between said semicylindrical portions and in a strip of dielectric material passed through said slots.

EUGENE T. HSU. 

